Sewing-machine feed mechanism



Get 17, 3950 K. HOHMANN SEWING MACHINE FEED mcnmzsm Filed April 6, 1948 IN VEN TOR.

M W H K W w R ATTORNEY I Patented Oct. 17,1950

' UNITED STATES PATENT OFFICE I I "2,526,480 v saw ng-MACHINE FEED liIEECHANISM I RichardK. Hohmann, Jamaica, N. Y. Application April 6, 1948, Serial No. 19,275

The general object of the present invention is to provide an improved sewing machine work feeding mechanism. More specifically, the object of the invention is to-'provide improved means for controlling the extent of feedingmovement of a sewing machine feed mechanism of the well known type including afeed bar carrying a feed dog and means for moving said feed bar in'the workfeeding direction' 'with the work engaging portions-of the feed dog elevated above the surface of the workload to thereby advance the work, and for movingthe feed dog in the opposite or non-feeding'directionwith the work engaging portions of the feed dog at a lower level atv which they are out'of operative engagement with the work.

A specific object ofthe invention is to provide a simple and effective mechanism for giving the feed dog the customary upanddown and horizontal to and fromovements, with, improved means for interrupting each workfeeding movee ment of the dog after an extent of feeding movement which may be varied to' thereby vary' the lengths of the individual stitches formed, made desirable by differences in the character of the work. The feeding movement is indirectly regulated by directly regulating the extent of the non-feeding or return movement given the feed bar. More precisely stated, a specific object of the invention is to provide simple and effective means by which non-feeding, or return, movement may be interrupted at the conclusion of a regulable portion of the full extent of such movement obtainable, without the tendency toshock and noise production whichasuch feeding movement interruption would'otherwise tend to oreate.

In the preferred form of attaining the object of the invention, I make use of an eccentric disc carried by the .hook shaft of the sewing machine, and engaging and moving surfaces of the feed bar to give the latter its up and down movements, and to move the feed bar, and thereby 2 Claims. (Cl. 112-215) I silientabutment carried by the feed bar with I a normally stationary abutment adjustably mounted on the sewing machine frame, in position to be engaged by the resilient abutment when the non-feeding movement of the feed bar has attained its desired extent. The various features of novelty which char acterize my invention are pointed outwith partticularity in the claims annexed to and forming apart of this specification. For a better under? standing of the invention;1however,"its: advan tages, and specific objects attained with its use,

reference should be had to the accompanying drawing and descriptive matter in which I have illustrated and described a preferred embodi-v ment of the invention.

Of, the'drawings: Fig. 1 is an elevation of sewingmachin'e, and

Fig. 2 is a perspective view of the feed bar and feed dog.

In th drawings, I have illustrated an embodiment of the present invention in a light weight, portable, chain stitch sewing machine of relatively small size and of the type disclosed and claimed in my co-pending application, Serial No. 19,275 filed of even date herewith. Said machine includes a frame comprising a base A, a'standard B and an arm C. Mounted in the frontend of the frame arm C is a vertical needle bar D, carrying a sewing machine needle D at its lower end, and a longitudinally movable tion A of the sewing machine frame and the the feed dog, longitudinally in the feeding direction against the action of a return or bias spring. The latter gives the feed bar its longitudinal movements in the return or non-feeding direction when the position of the eccentric permits.

In accordance with the present invention I provide the feed bar with a slightly yielding or resilient abutment in the'form of a strip of spring,

metal which extends transversely to the length of the feed bar. Each non-feedingor' return movement is arrested; afterthedesired extent of such ncw i e t,.v ytheengasement of the re:

hereinafter described feed dog L. Conventional means including a lever F pivoted at the front end of the sewing machine arm,'may be provided to raise the presser bar D and thus move the presser foot E out of operative engagement with the work moving over, the workbed A, when this is desirable. A hook G is carried by a horizontal rotating hook shaft G operatively connected to driving mechanism (not shown), which maybe of known form, andoperates to rotate the hook shaft and to give work penetrating and loop forming movements tothe needle D' in' timed relation to the relative movement of the hook shaft. as requiredifor the formation of chain stitches.

My improved feeding mechanism in the form shown, comprises a feed bar member H operatively associatedwith the hook shaft G and exthe front end of a tending transversely away from the latter in a generally horizontal direction toward the rear side of the machine. The feed bar is longitudinally movable, and its end adjacent the hook shaft is given up and down movements. The end of the feed bar remote from the hook shaft is in engagement with guiding means carried by the frame base A, and accommodating the longitudinal and the up and down movements of the feed bar. As shown, said guiding means comprises a post or guide pin I having one end anchored to the base A and extending through an open ended, longitudinally extending slot H. The post or guide pin I is parallel to the workbed surface A and may well have a threaded inner end screwed into the adjacent endwall of the sewing machine base, and have an enlarged head I at its front end in engagement with the front side of the feed bar portions at opposite sides of the slot H. The feed bar is biased for nonfeeding movement to the right by a bias spring J mounted in a recess inthe feed bar and acting as a compression spring between the shaft I and an abutment shoulder H of the feed bar. The end of the feed bar H remote from the post or shaft I is bifurcated to form spaced apart upper and lower legs. H having parallel adjacent sides which straddle a cam or disc K eccentrically mounted on the hook shaft and having adiameter equal to the distance between the parallel feed dog legs H The legs H are connected by an integral yoke portion of the feed bar, the surface of which is shown as a half cylinder curved about an axis midway between the legs H and having a radius length equal to one-half the distance between said legs.. 7

A feed dog L mounted-on the feed bar 1-! comprises two elevated, spaced apart, horizontally disposed work engaging bars L. Each of said bars has a serrated upper edge and is adapted for longitudinal movement in a corresponding slot M in a plate M which forms an extension of the workbed portion of the frame base A. The slots M and bars L are at opposite sides of the path of the needle, as the latter moves downward through a needle'hole in the plate M into the position in which the hook G can engage a loop forming portion of the thread extending between the needle and the work. During the feeding stroke of the feed bar, the work engaging bars L have their serrated upper edges above the level of the top surface of the work bed, and have lower portions received in said slots and moving longitudinally therein in the direction toward the rear side of the sewing machine. At the end of the working stroke, the cam lowers the adjacent end of the feed bar and thereby lowers the serrated work engaging bars L in the slots M so that the upper edges of the bars are below the top surface of the workbed during the longitudinal return or non-feeding movement of the feed bar. Thereafter the serrated bars L are again raised above the level of the top surface of the workbed preparatory to the next feeding movement of the feed bar.

In accordance with the present invention, the extent of movement of the feed bar in the feeding direction is regulated by the engagement of a resilient abutment member 0, secured to the feed bar, with an adjustable abutment member P mounted on the base portion of the sewing machine frame. The abutment member in the form shown is a thin metal strip extending across the space between the two legs and secured to the latter, with portions in abutting engagement 4 with the end surfaces of the legs H The abutment member P, as shown, is in the form of a lever P connected by a pivot P to the vertical end wall of the base portion of the sewing machine frame, and having a cam edge P which is adapted to engage the resilient abutment member O at a horizontal distance to the left of the pivot P which decreases or increases when the lever P is adjusted about the pivot in the clockwise or counterclockwise direction. The lever P is so mounted as to be frictionally maintained in any adjustment position given it until that adjustment is followed by a different adjustment. In the operation of the feeding mechanism, when the angular position of the cam K permits, the feed bar H is given a return or non-feeding longitudinal movement toward the cam by the bias spring J. Each such return movement of the feed bar is interrupted when the resilient abutment member 0 carried by the feed bar, engages the cam portion P of the abutment lever P. While the longitudinal feeding movements of the feed bar H are quite small, the tension of the spring J must be sufficient to insure the rapid repetition of those movements. In consequence, when each non-feeding longitudinal movement of the feed bar is arrested by the engagement of a rigid portion of the feed bar with a rigid stationary abutment such as is formed by the lever P, there is a tendency to undesirable shock and noise. Such shock and noise is avoided by the use of the resilient abutment memberYO, and in the practical operation of a sewing machine embodying the present invention, no vibration or tendency of the machine to creep or walk is apparent.

While in accordance with the provisions of the statutes, I have illustrated and described the best form of embodiment of my invention now 4i known to me, it will be apparent to those skilled in the art that changes may be made in the form of the apparatus disclosed without departing from the spirit of my invention, as set forth in the appended claims, and that in some cases certain features of my invention may be used to advantage without a corresponding use of other features. Having now described my invention, what I claim as new and desire to secure by Letters Pat- 5 ent, is:

1. The combination in a sewing machine comprising a frame including a base having a workbed portion, and an overhanging arm, and substantially parallel hook and needle bar shafts mounted in said base and arm respectively, of a feed mechanism comprising a cam mounted on said hook shaft, a feed bar elongated in a generally horizontal direction which is transverse to said shaft, guiding means carried by said frame for the end of said feed bar remote from said shaft, the end of the feed bar adjacent said shaft being formed with a bearing surface above and resting on said cam, and with a bearing surface between said remote end and said shaft and facing the latter, means biasing said feed bar for longitudinal movement toward said shaft, a metal strip extending transversely to the length of said feed bar and secured to the end of the latter adjacent said shaft and forming a vertically elongated resilient abutment portion of the feed bar, and an abutment member mounted on said frame at the opposite side of said cam from said guiding means in position to be engaged by said resilient abutment portion and to thereby arrest the movement of the feed bar toward said shaft and adjustable to vary the extent of longitudinal movement given the feed bar during each feeding operation.

2. The combination in a sewing machine comprising a frame including a base having a workbed portion, and an overhanging arm, and substantially parallel hook and needle bar shafts mounted in said base and arm, respectively, of a feed mechanism comprising a feed bar extending in a generally horizontal direction transverse to said hook shaft, guiding means carried by said frame for the end of said feed bar remote from said shaft, the end of the feed bar adjacent said shaft being bifurcated to form parallel spaced apart legs and a leg connecting the portion of the feed bar forming a bearing surface facing the hook shaft, a cam mounted on said hook shaft and extending between and engaging the adjacent sides of said legs, means biasing said feed bar for longitudinal movement toward said shaft and thereby tending to maintain said bearing surface in engagement with said cam, a metal strip extending transversely to said legs across the space between the latter and having its end bar toward said shaft, and adjustable to vary the extent of longitudinal movement given the feed bar, during each feeding operation.

RICHARD K. HOHMANN.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 42,036 Willcox Mar. 22, 1864 216,791 Grover June 24, 1879 373,164 Whitney Nov. 15, 1887 

